Disk drives, also called disk files, are information storage devices that use a rotatable disk with concentric data tracks containing the information, a head or transducer for reading and/or writing data onto the various tracks, and an actuator connected to a carrier for the head for moving the head to the desired track and maintaining it over the track centerline during read and write operations. The head may be a single-element inductive read/write head or a dual element inductive write/magnetoresistive read head. There are typically a number of disks mounted on a hub that is rotated by a disk drive or spindle motor, and a number of head carriers connected to the actuator for accessing the surfaces of the disks. A walled enclosure, including a base and a cover, supports the drive motor and head actuator and surrounds the heads and disks to provide a substantially sealed environment. The enclosure has a breather opening to equalize pressure differences between the drive interior and the ambient atmosphere, and provides a defined source of makeup air for enclosure leaks. A particulate filter is located near the breather opening to prevent particulate matter from entering the drive interior.
In conventional magnetic recording disk drives, the head carrier is an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a biasing force from a suspension that connects the slider to the actuator. The disk has a liquid lubricant film on its surface to minimize head and disk damage that may be caused by inadvertent slider-disk contact during operation, and to facilitate starting of the disk drive when the slider is at rest on the disk surface.
In contrast to conventional air-beating disk drives, contact or near-contact disk drives have been proposed that place the head carrier in constant or occasional contact with the disk or a liquid film on the disk during read and write operations. Examples of these types of disk drives are described in IBM's U.S. Pat. No. 5,202,803 and published European application EP 367510; U.S. Pat. No. 5,097,368 assigned to Conner Peripherals; and U.S. Pat. No. 5,041,932 assigned to Censtor Corporation.
Magnetic recording disk drives are very sensitive to chemical contaminants. High molecular weight organic vapors can adsorb on the very smooth surfaces of the disks and sliders and modify the properties of the liquid lubricant. Other chemical contaminants, such as SO.sub.2, may also induce corrosion of the metallurgy of the disks and heads, especially the magnetoresistive read elements. For these reasons, many disk drives use a chemical filter, in addition to a particulate filter, near the breather opening.
In conventional disk drives with a filter near the breather opening, the pressure gradient between the ambient atmosphere and the drive interior forces the air through the filter. This is desirable because it maximizes contact of the chemical vapors with the chemical filter material. The breather opening is typically located at the lowest pressure point in the drive to ensure that all air enters the drive through the breather filter attached to the breather opening. However, the impedance of a combined flow-through chemical and particle filter is increased by the addition of the chemical filter media. This can lead to contaminants entering the drive enclosure through other leaks or openings.
What is needed is a disk drive breather filter assembly that maximizes the gettering of chemical contaminants with the lowest possible flow impedance.